A phase-change thermal diode based on directional transport and its implementation method

Abstract

This invention provides a phase-change thermal diode based on directional transport and its implementation method. The phase-change thermal diode includes a tube wall, a directional transport capillary structure, a boiling-enhancing capillary structure, and a liquid working fluid. The inner side of the tube wall comprises the directional transport capillary structure and the boiling-enhancing capillary structure. The directional transport capillary structure functions to directionally transport the liquid working fluid; the boiling-enhancing capillary structure enhances boiling. The tube wall is in a vacuum or negative pressure environment and is filled with a compatible liquid working fluid. The directional transport capillary structure and the boiling-enhancing capillary structure are integrally formed by spin forming. This invention overcomes the shortcomings of existing phase-change thermal diodes, such as cumbersome fabrication processes, unsuitability for large-scale fabrication, and limited application range.

Description

Technical Field

[0001] This invention relates to the field of phase change thermal diode manufacturing technology, and in particular to a phase change thermal diode based on directional transport and its implementation method. Background Technology

[0002] Because thermal diodes are highly efficient unidirectional heat transfer elements, offering advantages such as controllable unidirectional heat transfer and high heat transfer efficiency, while also being power-independent, compact, and noiseless, they have found applications in various sectors of the national economy. In the aerospace field, they play a crucial role in dissipating heat from internal components. When exposed to sunlight, heat dissipation devices transfer heat in the reverse direction, potentially damaging electronic devices. Therefore, the emergence of unidirectional thermal diodes effectively protects electronic components.

[0003] The fabrication of directional transport capillary structures for existing phase-change thermal diodes is often limited by the shape of the tubular structure, resulting in the fabrication of unstructured gravity-based thermal diodes. However, gravity has a significant impact on these diodes, often causing them to malfunction in zero or low gravity environments. Therefore, developing a phase-change thermal diode with a simple fabrication process and good thermal polarity is of great importance to aerospace applications.

[0004] No invention patents addressing the aforementioned problems were found in publicly available literature and publications. The following inventions are somewhat related, with details as follows:

[0005] 1. "A Planar Thermal Diode, its Fabrication Method, and a Solar Collector," Application No.: CN202210156312.6, Publication / Announcement Date: 2022 / 05 / 24. This invention provides a planar thermal diode, its fabrication method, and a solar collector, relating to the field of thermal diode technology. Specifically, the planar thermal diode includes a hydrophilic plate, a hydrophobic plate, and a sealing element disposed between the hydrophilic plate and the hydrophobic plate; at least one closed cavity formed between the hydrophilic plate, the hydrophobic plate, and the sealing element is a water vapor region, which is used to carry the heat transfer medium; within the water vapor region, a capillary wick is disposed on the surface of the hydrophilic plate. The planar thermal diode of this invention has excellent unidirectional heat transfer capability and reverse heat insulation capability, controllable energy transfer direction, and high heat transfer efficiency; it also has a certain degree of designability and can meet the heat transfer requirements of different scenarios.

[0006] 2. Application No. CN202310453983.3, Publication / Announcement Date: 2023 / 08 / 01, entitled "An Adaptive Thermal Diode and Its Manufacturing Method". This invention provides an adaptive thermal diode and its manufacturing method. The adaptive thermal diode includes an upper cover and a lower shell that interlock, forming a sealed fluid channel cavity between them. Within the lower shell, from left to right, are an evaporation end, a silicon substrate, and a condensation end. Multiple trenches arranged in a linear array are formed on the silicon substrate. The depth and width of each trench gradually decrease from the evaporation end to the condensation end, creating a wedge-shaped structure between adjacent trenches. The upper surface width of each wedge-shaped structure gradually increases from the evaporation end to the condensation end. The trenches and wedge-shaped structures cooperate to form a microchannel structure with gradient wettability. The adaptive thermal diode provided by this invention enables the heat dissipation medium to move adaptively in the horizontal direction to successfully return to the condensation end, allowing the thermal diode to achieve unidirectional heat transfer in different directions.

[0007] 3. Application No. CN202210340929.3, Publication / Announcement Date: 2023 / 03 / 14, entitled "A Gravity-Type Thermal Diode Based on Porous Media and Hydrophobic Surface". This invention relates to a gravity-type thermal diode based on a porous media and a hydrophobic surface. The gravity-type thermal diode includes: a sealed heat-conducting shell and a porous capillary wick medium. The inner wall of one side of the heat-conducting shell is fully covered with the porous capillary wick medium, and the inner wall of the other side of the heat-conducting shell is coated with a hydrophobic coating. The interior of the heat-conducting shell is a vacuum cavity, and the bottom of the heat-conducting shell contains a small amount of purified water to remove dissolved gases. This design not only achieves directional heat conduction and effectively reduces indoor heating energy consumption, but also has a reasonable structural design and realizes the environmentally friendly utilization of atmospheric heat energy.

[0008] 4. Application No. CN202310631869.5, Publication / Announcement Date: 2024 / 02 / 20, entitled "A Graded Start-up Thermal Diode and Its Processing Method". This invention relates to the field of heat pipe technology, and particularly to a graded start-up thermal diode, comprising an outer tube. The outer tube has three mutually sealed and independent cavities arranged sequentially along the axial direction: a first cavity, a second cavity, and a third cavity. Each cavity is connected to a liquid-filling pipe communicating with its interior. Each cavity is filled with a different heat transfer medium, and each cavity is equipped with a liquid-absorbing core for transferring the working medium. This heat pipe can only transfer heat in a specific heat transfer direction; heat transfer in the opposite direction is not possible. Furthermore, unlike traditional thermal diodes, this invention controls the properties of the internal working heat transfer medium to achieve low-temperature heat operation and graded start-up unidirectional heat transfer. It can achieve unidirectional heat transfer not only under zero-gravity conditions but also over long distances. This invention also provides a processing method for the graded start-up thermal diode.

[0009] 5. Application No. CN202210025916.7, Publication / Announcement Date: 2022 / 05 / 13, entitled "A Tesla Valve-Type Ultrathin Planar Thermal Diode Based on Phase Change Heat Transfer Technology". This invention relates to a Tesla valve-type ultrathin planar thermal diode based on phase change heat transfer technology, comprising a tube body. Within the tube body are an evaporation end, a liquid working fluid chamber, a Tesla valve flow channel, a liquid-absorbing core filled with liquid working fluid, and a condensation end. The liquid-absorbing core is disposed within the liquid working fluid chamber. The condensation end, liquid-absorbing core, and evaporation end are sequentially connected to form a liquid working fluid passage, and the evaporation end, Tesla valve flow channel, and condensation end are sequentially connected to form a gaseous working fluid passage. The unidirectional thermal conductivity of the ultrathin planar thermal diode is improved by utilizing the acceleration characteristics of the Tesla valve and its unidirectional conductivity. During forward heating, the gaseous working fluid flows from the evaporation end to the condensation end, flowing in the same direction within the Tesla valve, resulting in low gas resistance and high thermal conductivity. During reverse heating, the gaseous working fluid flows from the condensation end to the evaporation end, flowing in the opposite direction within the Tesla valve, resulting in high gas resistance and low thermal conductivity. This achieves the effect of a thermal diode and can be widely used in the microelectronics industry.

[0010] Patent 1 utilizes the hydrophilic structure on the surface of the structure to achieve unidirectional heat transfer; Patent 2 utilizes the inclined condenser end and the V-shaped groove on the substrate to achieve unidirectional liquid transfer; Patent 3 utilizes the hydrophilic and hydrophobic surfaces of the structure and gravity to achieve unidirectional heat transfer; Patent 4 utilizes the method of segmenting the heat pipe and filling it with working fluids of different boiling temperatures to achieve unidirectional heat transfer from the low-boiling-point working fluid segment to the high-boiling-point working fluid segment; Patent 5 utilizes the unidirectional conductivity of the Tesla valve to achieve unidirectional heat conduction. Summary of the Invention

[0011] The technical problem solved by this invention is to provide a phase change thermal diode structure based on directional transport, which overcomes the shortcomings of existing phase change thermal diodes, such as cumbersome preparation process, unsuitability for large-scale preparation, and limited application range.

[0012] The second technical problem solved by the present invention is to provide a method for fabricating a phase change thermal diode structure based on directional transport.

[0013] The solution of this invention is: a phase change thermal diode structure based on directional transport, characterized in that it comprises a tube wall, a directional transport capillary structure, a boiling-enhancing capillary structure, and a liquid working fluid; the directional transport capillary structure is located on the inner side of the tube wall in the heat source contact area and has the function of directional transport of the liquid working fluid; the boiling-enhancing capillary structure is located on the inner side of the tube wall in the heat source contact area and has the function of enhancing boiling; the inside of the tube wall is a vacuum or negative pressure environment and is filled with a compatible liquid working fluid; the directional transport capillary structure and the boiling-enhancing capillary structure are integrally formed by spinning.

[0014] Preferably, the pipe wall is made of metal materials such as copper, aluminum, or stainless steel;

[0015] Preferably, the liquid working medium is a liquid compatible with the pipe wall. For example, if copper is used, the liquid working medium can be deionized water, ethanol, or other working media.

[0016] Preferably, the directional transport capillary structure and the boiling-enhanced capillary structure are formed by spinning on the inner side of the tube wall;

[0017] Preferably, the directional transport capillary micron-sized V-shaped prisms are uniformly arranged along the diode axis or arranged in an Archimedean spiral along the tube wall.

[0018] Preferably, the boiling-enhanced capillary structure consists of spherical protrusions that are uniformly arranged along the diode axis or arranged in an Archimedean spiral pattern along the tube wall.

[0019] Preferably, the spin-forming mandrel is composed of two wedge-shaped semicircular rods, and the surface of the spin-forming mandrel has a directional transport capillary inversion structure and a boiling-enhanced capillary inversion structure, both of which are obtained by laser milling.

[0020] The method for fabricating a phase-change thermal diode based on directional transport includes the following steps:

[0021] (1) Preparation of the spin-shrink mandrel: The directional transport capillary inverse structure and the boiling-enhanced capillary inverse structure are milled on the surface of the mandrel by laser. The corresponding length is determined by the specific working requirements of the thermal diode. At the same time, the mandrel is cut into a wedge shape diagonally by wire cutting. The mandrel is fixed in the thermal diode shell by the opposite movement of the wedge plane.

[0022] (2) Preparation of tube wall with capillary structure: The preparation of directional transport capillary structure and boiling-enhanced capillary structure is achieved by using existing heat pipe spinning equipment.

[0023] (3) Enhanced treatment: The directional transport capillary structure is hydrophobic and the boiling-enhanced capillary structure is hydrophilic to further enhance the heat transfer capacity.

[0024] (4) Shell sealing: A certain length of shell is cut off, and one end of the shell is sealed by shrinking and spot welding. The other end is only shrunk to form a small-diameter shell for liquid injection.

[0025] (5) Liquid injection and degassing: A certain amount of liquid working fluid is injected into the heat pipe using an injection system, and the thermal diode is fabricated through primary and secondary degassing.

[0026] (6) Post-processing of thermal diodes: The thermal diodes are straightened and shaped to meet the requirements, and surface treatment is achieved through cleaning, anti-oxidation treatment, etc.

[0027] The advantages of this invention compared to the prior art are:

[0028] (1) The internal structure of the phase change thermal diode based on directional transport is simple. The directional transport capillary structure and the boiling-enhanced capillary structure are integrally formed by spinning, which further enhances the heat transfer capability of the thermal diode.

[0029] (2) The thermal diode fabrication process of the present invention adopts the copper water heat pipe process, which promotes the maturation of the thermal diode fabrication process and enables the mass production of phase change thermal diodes. Attached Figure Description

[0030] Figure 1 A cross-sectional schematic diagram of a phase-change thermal diode structure based on directional transport;

[0031] Figure 2 Based on a schematic diagram of a spin mandrel;

[0032] Figure 3 A schematic diagram of the spin forming process for a phase-change thermal diode for directional transport;

[0033] In the diagram, 1. tube wall; 2. directional transport capillary structure; 3. boiling-enhanced capillary structure; 4. directional transport capillary inverse structure; 5. boiling-enhanced capillary inverse structure; 6. spin mandrel; 7. ball bearing. Detailed Implementation

[0034] The present invention will be further described below with reference to the embodiments.

[0035] like Figures 1-3As shown, a method for fabricating a phase-change thermal diode based on directional transport includes: a tube wall 1, a directional transport capillary structure 2, a boiling-enhanced capillary structure 3, and a compatible liquid working fluid; a ball bearing 7 is thermally spun on the outer surface of the tube shell 1, copying the directional transport capillary inverse structure 4 and the boiling-enhanced capillary inverse structure 5 on the surface of the spun mandrel 6 onto the inner wall of the tube shell, thus fabricating the directional transport capillary structure 2 and the boiling-enhanced capillary structure 3. Then, a phase-change thermal diode based on directional transport is formed through a conventional heat pipe process.

[0036] The intelligent spin mandrel 6 consists of two wedge-shaped semicircular rods. The surface of the spin mandrel has a directional transport capillary inverse structure 4 and a boiling-enhanced capillary inverse structure 6, both of which are obtained by laser milling. The wedge-shaped structure of the intelligent spin mandrel achieves close contact between the mandrel and the tube shell through opposing clamping.

[0037] Example 1

[0038] A phase-change thermal diode structure based on directional transport and its fabrication method include the following steps:

[0039] (1) Spinning mandrel preparation: Directional transport capillary inverse structure 4 and boiling-enhanced capillary inverse structure 5 are milled on the surface of the spinning mandrel 6 by laser. The corresponding lengths are determined by the specific working requirements of the thermal diode. At the same time, the mandrel is cut into a wedge shape diagonally by wire cutting. The mandrel is fixed in the thermal diode shell by the opposite movement of the wedge plane.

[0040] (2) Preparation of tube wall with capillary structure: Using existing heat pipe spinning equipment, the ball 7 is thermally spun on the outer surface of the tube shell 1 to realize the preparation of directional transport capillary structure 2 and boiling-enhanced capillary structure 3.

[0041] (3) Enhanced treatment: The directional transport capillary structure 2 is hydrophobic, and the boiling-enhanced capillary structure 3 is hydrophilic to further enhance the heat transfer capacity.

[0042] (4) Shell sealing: A certain length of shell is cut off, and one end of the shell is sealed by shrinking and spot welding. The other end is only shrunk to form a small-diameter shell for liquid injection.

[0043] (5) Liquid injection and degassing: A certain amount of liquid working fluid is injected into the heat pipe using an injection system, and the thermal diode is fabricated through primary and secondary degassing.

[0044] (6) Post-processing of thermal diodes: The thermal diodes are straightened and shaped to meet the requirements, and surface treatment is achieved through cleaning, anti-oxidation treatment, etc.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to the embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

[0046] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A phase change heat diode based on directional transport, characterized by: The pipe wall, the directional transport capillary structure, the boiling enhancement capillary structure and the liquid working medium are included. The inner side of the pipe wall is the directional transport capillary structure and the boiling enhancement capillary structure. The directional transport capillary structure has the function of directional transport of the liquid working medium. The boiling enhancement capillary structure has the function of enhancement of boiling.

2. The diode of claim 1, wherein: The inner side of the pipe wall is a vacuum or negative pressure environment, and is filled with compatible liquid working medium.

3. The diode of claim 2, wherein: The directional transport capillary structure and the boiling enhancement capillary structure are integrally formed by spinning.

4. The diode of claim 2, wherein: The directional transport capillary structure is a plurality of micron-level V-shaped prisms uniformly arranged along the diode axis or arranged in an Archimedes spiral along the pipe wall.

5. A method of fabricating a directional transport based phase change thermal diode structure as claimed in claim 1, wherein The boiling enhancement capillary structure is a plurality of spherical protrusions uniformly arranged along the diode axis or arranged in an Archimedes spiral along the pipe wall. The pipe wall is made of metal material. The metal material includes copper, aluminum and stainless steel. The liquid working medium is compatible with the pipe wall. The preparation of the spinning shrinkage mandrel includes milling the directional transport capillary structure and the boiling enhancement capillary structure on the surface of the mandrel. The preparation of the pipe wall with the capillary structure includes fixing the spinning shrinkage mandrel in the pipe shell with smooth inner wall, and preparing the directional transport capillary structure and the boiling enhancement capillary structure on the inner wall of the pipe shell by the heat pipe spinning equipment. The strengthening treatment includes hydrophobic treatment for the directional transport capillary structure and hydrophilic treatment for the boiling enhancement capillary structure.

6. The method of claim 5, wherein: The shell plate sealing includes cutting a certain length of the pipe shell, sealing one end of the pipe shell by spinning and spot welding, and only spinning the other end of the small diameter pipe shell to note the liquid.

7. The method of claim 5, wherein: The liquid injection and degassing includes injecting the liquid working medium into the heat pipe, and preparing the heat diode by primary degassing and secondary degassing.

8. The method of claim 5, wherein: The heat diode post-processing includes rolling and shaping the heat diode to meet the requirements, and surface treatment by cleaning and anti-oxidation treatment. The spinning shrinkage mandrel is cut into a wedge shape along the diagonal by wire cutting, and the mandrel is fixed in the heat diode shell by the opposite movement of the wedge planes. The directional transport capillary structure and the boiling enhancement capillary structure on the surface of the spinning shrinkage mandrel are obtained by laser milling. The directional transport capillary structure and the boiling enhancement capillary structure are integrally formed based on the spinning process.

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